1. Field of the Invention
The present invention relates to an indication lamp and more particularly to an indication lamp having a translucent indication portion and used in aircraft passenger cabins.
2. Prior Art
Indication lamps are used in a passenger cabin of an aircraft so as to prompt passengers to, for instance, refrain from smoking and to fasten their seat belts. An incandescent lamp has conventionally been used as a light source for such passenger cabin indication lamps.
FIG. 7 shows a typical indication lamp of this kind.
The indication lamp is constructed by a plurality of incandescent lamps 110A and 110B mounted on printed wiring boards 108A and 108B, respectively, housed in two lamp chambers 106A and 106B formed by a housing 102 and a front cover 104. Translucent indication portions 112A and 112B that allow part of the light from the incandescent lamps 110A and 110B to pass through are formed on the front cover 104 so as to be in front of the lamp chambers 112A and 112B. When the incandescent lamps 110A in the lamp chamber 106A are lit, the incandescent lamps 110A illuminate the translucent indication portion 112A from behind to give a non-smoking sign indication. When the incandescent lamps 110B in the lamp chamber 106B are lit, the incandescent lamps 110B illuminate the translucent indication portion 112B from behind to give a seat belt fastening sign indication.
In the above conventional indication lamp that uses an incandescent lamp as a light source thereof, however, a filament thereof tends to be broken due to vibrations and other causes acting on the aircraft. On top of that, the life of the incandescent lamp (approximately 200 hours) is generally extremely short when compared to the useful life of aircraft (approximately 73,000 hours), which makes it necessary to replace the incandescent lamp frequently.
White light emitting diodes can be used instead as the light source of the indication lamp. Such diodes can extend the life of indication lamps greatly (approximately 30,000 hours) compared to the incandescent lamp, making it generally possible to solve the above problem.
However, the white light emitting diode emits a white light of a cool color, not like a soft light of a warm color emitted by incandescent lamps. It gives the passenger who looks at the translucent indication portions 112A and 112B a cold impression, presenting a visibility problem.
If the light source for only a part of a plurality of indication lamps disposed in the passenger cabin is changed to white light emitting diodes, that particular indication lamp lights up in a different color from other indication lamps whose light sources are incandescent lamps, causing an inferior visual impression.
Such problems arise not only from the indication lamps provided in passenger cabins of aircraft, but also from general indication lamps that have translucent indication portions.
Accordingly, the object of present invention is to provide an indication lamp having a translucent indication portion, in which the life of a light source is significantly extended and, at the same time, a visibility of the translucent indication portion can be enhanced.
The present invention accomplishes the above object by way of using as light sources a plurality of light emitting diodes of different colors of illumination, thus obtaining a color similar to a light emitted by an incandescent lamp with a mixture of colors emitted by such light emitting diodes.
The above object is accomplished by a unique structure of the present invention for an indication lamp that has a light source and a front cover on which a translucent indication portion of a predefined shape that allows a part of light from the light source to pass through is formed; and the unique structure of the present invention is that the light source is formed with a plurality of light emitting diodes that have different colors of illumination, and these light emitting diodes are designed to light up simultaneously so as to illuminate a mixture of colors that is similar to a light emitted by an incandescent lamp.
In the above structure, the indication lamp may be constructed by only a single light source of a plurality light emitting diodes or a plurality of light sources.
Also, in regards to the plurality of light emitting diodes, the color of illumination of each light emitting diode, the number of light emitting diodes used, the disposition of the light emitting diodes, and other specific arrangements are not limited as long as they illuminate, when lit, a mixture of colors similar to the light emitted by the incandescent lamp.
The phrase xe2x80x9cdifferent colors of illuminationxe2x80x9d used in the above means that not all of the light emitting diodes emit the same color. Two or more light emitting diodes that emit the same color of illumination can be employed in the present invention.
Furthermore, the phrase xe2x80x9ca mixture of colors similar to a light emitted by an incandescent lampxe2x80x9d more specifically means a color that falls within the regions of 0.37xe2x89xa6xxe2x89xa60.60 and 0.34xe2x89xa6yxe2x89xa60.50 in the CIE chromaticity diagram.
It is preferable that the color is within the regions of 0.42xe2x89xa6xxe2x89xa60.57 and 0.38xe2x89xa6yxe2x89xa60.46.
As described above, the indication lamp according to the present invention comprises a plurality of light emitting diodes having different colors of illumination as the light source, and these light emitting diodes light up simultaneously and illuminate a mixture of colors similar to the light emitted by the incandescent lamp.
Accordingly, since the lamp comprises a plurality of light emitting diodes, the life of the light source can be extended greatly compared to the conventional structure that uses incandescent lamps. The extended life of the light source is even further assured because in the present invention a single-color light emitting diode with a life (approximately 100,000 hours) that is even longer than a white light emitting diode is employed, instead of the white light emitting diode, as the light emitting diodes that form the light source. Furthermore, in the indication lamp of the present invention, a plurality of light emitting diodes light up simultaneously so as to illuminate a mixture of colors similar to or the substantially the same as the light emitted by the incandescent lamp. Thus, the translucent indication portion of the front cover is illuminated by a soft light of a warm color which is like a light emitted by incandescent lamps.
Accordingly, with the indication lamp that has the translucent indication portion in the front cover according to the present invention, it is possible to significantly extend the life of the light source and, at the same time, to enhance the visibility of the translucent indication portions.
In cases where a plurality of indication lamps are disposed as in the passenger cabin of an aircraft, and where a part of the light sources for these indication lamps is changed from the conventional incandescent lamps to a plurality of light emitting diodes, such indication lamps can be prevented from being seen in a color significantly different from the color of the remaining indication lamps.
As described above, there is no limitation to a specific configuration of each light emitting diode that forms the plurality of light emitting diodes. It is nonetheless easy to accomplish the illumination of a mixture of colors similar to the color of the incandescent lamp by way of forming the light emitting diodes with red light emitting diodes and green light emitting diodes.
A red translucent indication portion can be formed in part of the translucent indication portion. With this red translucent indication portion, it is possible to illuminate the portions other than the red translucent portion with a color similar to the color of the incandescent lamp and, at the same time, to illuminate the red translucent portion with red that is more vivid than the color emitted by the red light emitting diode when the light sources are lit.
The above-described light sources may be designed so that all the light emitting diodes that form the light sources are lit simultaneously. A light-up mode can be established so that it comprises a simultaneous light-up mode, in which both the red light emitting diodes and the green light emitting diodes are lit at the same time, and a green light-up mode, in which only the green light emitting diodes are lit. This light-up mode design provides significant operational advantages. In the simultaneous light-up mode, the red translucent portion is illuminated in red, while the remaining portions are illuminated with a color similar to the incandescent light. In the green light-up mode, on the other hand, the red translucent portion is not illuminated, while the remaining portions are illuminated in green. Accordingly, viewers or can easily know that there has been a change in the light-up mode of the indication lamp.